Tetrapedia diversipes Klug is herein reported for the first time to be the host of the cleptoparasite Coelioxoides waltheriae Ducke. Because these two genera had been previously recognized as sister taxa [A. Roig-Alsina. 1990. Coelioxoides Cresson, a parasitic genus of Tetrapediini (Hymenoptera: Apoidea). Journal of the Kansas Entomological Society 63: 279–287], the authors wished to learn to what extent biological information and immature stages reflected this relationship. Tetrapedia diversipes normally nests in holes in wood such as old beetle burrows, and it was induced to use trap nests for this study. Many aspects of the nesting behavior of females of this species are described, including the following: diurnal flight period; sleeping habits; nest structure; nest provisioning; egg placement; and sequence of nest construction, provisioning, and oviposition. Eggs produced by this species are categorized as “giant” (K. Iwata and S.F. Sakagami. 1966. Gigantism and dwarfism in bee eggs in relation to the mode of life, with notes on the number of ovarioles. Japanese Journal of Ecology 16: 4–16). Its first instar was discovered to be pharate within the chorion while the following four instars actively feed. Defecation starts early in the last larval stadium. Females use floral oils both in nest construction and in provisioning, and they carry pollen, oil, and soil with their scopae. The biology of T. diversipes was compared with that of other species in the genus and then compared with that of other apines that are known to nest in preformed cavities and that provision nests with pollen and floral oils.

The host-nest searching behavior of Coelioxoides waltheriae is described. The cleptoparasite introduces its egg into the closed cell of the host shortly after cell closure. This egg is characterized as “small” (Iwata and Sakagami, ibid.) and has a very short incubation period. The highly modified first instar immediately feeds on the host egg and grows remarkably fast on the host yolk. This species has only four instars.

Rates of development of the host and cleptoparasite are compared. Both have four ovarioles per ovary. Eggs, first instars, last larval instars, and pupae of host and cleptoparasite are taxonomically described and compared. In conclusion, the immatures of Coelioxoides and Tetrapedia are quite distinct from those of other known apids. While these two genera are probably sister genera based on the similarities identified by Roig-Alsina (op. cit.) and by this study, they are quite different from one another based on features of the eggs, first instars, and pupae.